<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>页面渲染性能优化</title>
  <style>
    body{
      background: red;
    }
  </style>
</head>
<body>
  <div id="app">
    121212
  </div>
  <script src="./src/3.longtask.js"></script>
  <script>
    for (var index = 0; index < 1000000000; index++) {
     
    }
  </script>
</body>
</html>